These studies are directed toward further study of the efficacy and safety of optimal doses of chenodeoxycholic acid therapy for dissolving gallstones and biliary duct stones. Second, we will continue to evaluate the medium chain monoglyceride, mono-octanoin, to further characterize its safety and efficacy for dissolving retained retained biliary duct stones. Thirdly, the pharmacologic effects and efficacy of ursodeoxycholic acid ingestion in patients with ileal resection will be characterized with the objective of evolving improved therapy for these patients with regard to their predisposition for cholesterol gallstone, malabsorption, and diarrhea. Lastly, we will study the intermediary metabolism of ursodeoxycholic acid and chenodeoxycholic acid using deuterated bile acids.